1. Entomology
Chapter 12

2. Entomology Study of insects and arthropods
Invasion in foods consumed by humans
Improper use of pesticides
Determine postmortem interval (PMI) of corpse
Time of death

3. Determining Time of Death (PMI)
Determined by presence of species of insects and arthropods
Blowflies arrive quickly and first
Lay eggs near moist areas of the body (eyes, mouth, nose, open wounds)
Larva (maggots) go through three different stages of growth (instars) on the body
First instar occurs 8 hours after egg is laid
Second instar occurs 20 hours later
Third instar occurs 20 hours later
After 5 days, larva stops feeding and rests
After a few more days, larva become pupa
After 3 weeks since the egg was laid, adult flies emerge

4. Other Factors affecting PMI estimates
Weather
Body enclosed or wrapped
Presence of drug or poisons

5. Body Decomposition and Arthropods
Necrophages
Insects that feed on the corpse tissue
Flies
Omnivores
Feed on body and other insects on corpse
Wasps and beetles
Predators & Parasites
Feed on insects on corpse
Incidentals
Insects that use the body as their normal habitat (make it their home)
Spiders, centipedes, mites

6. Stages of Decomposition
Fresh
1-2 days
Adult blowflies, fresh flies and yellowjackets
Bloated
2 - 6 days
Blowflies, flies, beetles, yellowjackets
Decay
5 – 11 days
Flies, beetles, cockroaches
Postdecay
10 – 24 days
Fruit flies, gnats, beetles, flies
Dry stage
24+ days
Ants, flies, beetles

7. Blow Fly Metamorphosis
Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages.
1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc.
2nd – Eggs hatch into larva (maggots) in hours.
3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages.
1st Instar - 5 mm long after 1.8 days
2nd Instar - 10 mm long after 2.5 days
3rd Instar – mm long after 4-5 days
4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil.
5th – Adult flies emerge from pupa cases after 6-8 days.
Adult
Pupa
Eggs
3rd Instar Larva
1st Instar Larva
2nd Instar Larva
It takes approximately days from egg to adult depending on the temperatures and humidity levels at the location of the body.
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8. Entomologist Evidence Collection
Collect insects on and around body
Help determine sight of trauma
Help determine cause of death
Can use insects and perform toxicology